I am installing a ceiling fan to replace a ceiling light. The wiring up there is old. Three red are twisted together and live. two black are twisted together and not live. One futher black is by itself and live. Turning on/off the wall light switch does not change what is live. The fan expects live / neutral / earth. How should I wire this please.
Operating the light switch must change the live connection otherwise your original light would have been on all the time. The most likely arrangement will be leave the 3 reds together and terminate in a block.
Connect the fan neutral to the two blacks which are twisted together and the fan live to the single black wire. If there is no earth you should provide one.